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GPS Week Number Rollover

  [TSB17540] Show Article Properties


Alert Type:
PSN - Product Support Notification
Product Affected:
ACX, BTI, E, EX, M, MX, PTX, T, VMX, VRR, Vsrx, QFX, SRX, NFX
Alert Description:

The purpose of this Product Support Notification is to clarify the effect of GPS Week Number Roll Over (WNRO) for Juniper Networks's active products.
 

Background information

The GPS Week Number count began at approximately midnight on the evening of 05 January 1980 / morning of 06 January 1980. Since that time, the count has been incremented by 1 each week and broadcast as part of the GPS message. The GPS Week Number field is modulo 1024. This means that at the completion of week 1023, the first GPS week number rolled over to 0 on midnight GPS Time of the evening of 21 August 1999 / morning of 22 August 1999. Note that this corresponded to 23:59:47 UTC on 21 August 1999. The second GPS week number rollover will happen on 6 April 2019.

Juniper Networks' Product with an Embedded Receiver

The ACX500 series has an embedded GPS receiver - Trimble 'Res SMT 360' with firmware version 1.04. According to Trimble's Product Bulletin number 02-003-JD11-2018, the 'Res SMT 360' receiver with firmware version 1.04 has been tested for WNRO. The result of the test shows the 'Res SMT 360' continues to provide the correct date and time across WNRO events until August 9th, 2036.

Juniper Networks' Products without an Embedded Receiver

Juniper Networks' Products support the following time-related functionalities. 
  1. Network Time Protocol - NTP
  2. Precision Time Protocol PTP
  3. Centralized Clocking interface with GPS clock source
The effect of GPS WNRO on NTP and PTP depends largely on the "Grandmaster" (master) clock sources. Please ensure that the master clock source has been tested to provide the correct date and time across WNRO events.

For "Centralize Clocking interface with GPS clock source", in this mode, our system can use BITS clock source or the clock signals from a GPS receiver.  If you are using the clock signals from a GPS receiver. Please contact the GPS manufacturers to make sure that your clock signals from the GPS are not affected by the WNRO events.
Solution:
  • ACX500 with embedded Trimble 'Res SMT 360' GPS receiver has been tested that it continues to provide the correct date and time across WNRO events until August 9th, 2036. Therefore there is no intervention needed for the 2019 GPS WNRO event.
  • NTP and PTP functionalities. These protocols depend on having accurate and resilient grandmaster clock sources. Please read the best practice document prepared by the US-CERT.gov. The best practices guide is called the "Best Practices for Improved Robustness of Time and Frequency Sources in Fixed Locations". We provide a copy of this guide at the end of this bulletin.
  • Centralize Clocking interface with GPS clock source - Please contact the GPS manufacturers to make sure that the GPS clock signals are not affected by the WNRO events. 
Modification History:
First publication 2019-03-28
Related Links:
Attachment File:
SMT 360_GG WNRO_02-003-JD11-2018[2].pdf
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